Ls

The meaning of «ls»

In computing, ls is a command to list computer files in Unix and Unix-like operating systems. ls is specified by POSIX and the Single UNIX Specification. When invoked without any arguments, ls lists the files in the current working directory. The command is also available in the EFI shell.[1] In other environments, such as DOS, OS/2, and Microsoft Windows, similar functionality is provided by the dir command. The numerical computing environments MATLAB and GNU Octave include an ls
function with similar functionality.[2][3]

An ls utility appeared in the first version of AT&T UNIX, the name inherited from a similar command in Multics also named 'ls', short for the word "list".[4][5][6] ls is part of the X/Open Portability Guide since issue 2 of 1987. It was inherited into the first version of POSIX.1 and the Single Unix Specification.[7]

Today, the two popular versions of ls are the one provided with the GNU coreutils package, and that released by various BSD variants. Both are free software and open source, and have only minor syntax differences. The version of ls bundled in GNU coreutils was written by Richard Stallman and David MacKenzie.[8]

Unix and Unix-like operating systems maintain the idea of a current working directory, that is, where one is currently positioned in the hierarchy of directories. When invoked without any arguments, ls lists the files in the current working directory. If another directory is specified, then ls will list the files there, and in fact the user may specify any list of files and directories to be listed.

Files whose names start with "." are not listed, unless the -a flag is specified, the -A flag is specified, or the files are specified explicitly.

Without options, ls displays files in a bare format. This bare format however makes it difficult to establish the type, permissions, and size of the files. The most common options to reveal this information or change the list of files are:

It's normally possible to highlight different types of files with different colors, instead of with characters as -F would, but this is an area where the two main ls versions differ:

When the option to use color to indicate file types is selected, the output might look like:

The following example demonstrates the output of the ls command given two different arguments (pwd is a command that shows the present working directory, or in other words, the folder you are currently in):